The present invention relates to a mass flow controller, commonly termed MFC. More particularly, the present invention provides a novel technique including a device and method for maintaining a fluid flow rate of fluids used in, for example, semiconductor processing or the like. Merely by way of example, the present invention is illustrated using a device and methods related to integrated circuit processing. But it will be recognized that the present invention also can be applied to the manufacture of products such as flat panel displays, hard disk drives, and others.
In the manufacture of semiconductor integrated circuits, process complexity and wafer size tends to increase with time. For instance, wafer size has increased from one inch up to six inch over the past thirty years. Larger sized wafers such as eight inch are now being used. Twelve inch wafers and larger are being proposed. As wafer size and complexity of processing increase, gases used for the manufacture of the integrated circuits also become more important. In particular, control of a selected flow rate range for a process step (e.g., plasma etching ("PE"), chemical vapor deposition ("CVD")) becomes rather important. Accordingly, mass flow controllers have been used to selectively control fluid flow rates of selected process steps.
Numerous mass flow controllers are presently on the market today. Manufacturers of mass flow controllers include, among others, Unit Instruments, Inc. ("Unit"), Brooks Instruments ("Brooks"), and Tylan General ("Tylan"). These manufacturers generally have a broad range of products to cover a variety of flow ranges, which are used in the manufacture of integrated circuit devices. For instance, Unit has at least ten different products for the purpose of covering a variety of flow rate ranges. Tylan has at least seven different products. As for Brooks, it has about eight products or more for covering different fluid flow ranges.
A limitation with these conventional mass flow controllers is their sheer number, where each controller can often be used for a limited fluid flow range. The sheer number of these mass flow controllers often translates into large numbers of different controller units being used and stored for replacement in the manufacturing line or semiconductor fabrication plant, commonly termed wafer fab. Accordingly, it is often quite expensive and time consuming to keep available all necessary spare parts to replace faulty or broken mass flow controllers.
Additionally, conventional mass flow controllers can often be adjusted to accommodate a relatively narrow flow rate range, which makes it often impossible or highly impractical to modify such conventional mass flow controllers to accommodate a different and often higher fluid flow rate. Therefore, companies such as Unit generally introduce a new mass flow controller to replace pre-existing controllers. This replacement process often translates into discarding older mass flow control units for newer ones at the expense of the wafer fab or wafer manufacturer.
From the above, it is seen that a mass flow controller which is cost effective and efficient is often desirable.